# comment 评论；意见；批评；描述
1,新建表以及添加表和字段的注释.
create table t_user(
ID INT(19) primary key auto_increment comment ‘主键‘,
NAME VARCHAR(300) comment ‘姓名‘,
CREATE_TIME date comment ‘创建时间‘
)comment = ‘用户信息表‘;
# 字段内在字段最后面添加COMMENT 注释 ,括号外面用COMMENT=‘‘来给表添加注释
2,修改表/字段的注释.
alter table t_user comment = ‘修改后的表注释信息(用户信息表)‘;
alter table t_user modify column id int comment ‘主键ID‘;
--注意：字段名和字段类型照写就行
3,查询数据库所有表的详细信息(包括表的注释).
use information_schema;
select * from TABLES where TABLE_SCHEMA=‘你的表所在的数据库‘;
--查询某一张表的
use information_schema;
select * from TABLES where TABLE_SCHEMA=‘你的表所在的数据库‘ and TABLE_NAME= ‘你的表名‘;
mysql> SELECT * FROM TABLES WHERE table_schema=‘test‘ AND table_name=‘test1‘\G
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: test1
TABLE_TYPE: BASE TABLE
ENGINE: InnoDB
VERSION: 10
ROW_FORMAT: Dynamic
TABLE_ROWS: 0
AVG_ROW_LENGTH: 0
DATA_LENGTH: 16384
MAX_DATA_LENGTH: 0
INDEX_LENGTH: 0
DATA_FREE: 0
AUTO_INCREMENT: NULL
CREATE_TIME: 2020-03-26 22:47:59
UPDATE_TIME: NULL
CHECK_TIME: NULL
TABLE_COLLATION: utf8_general_ci
CHECKSUM: NULL
CREATE_OPTIONS:
TABLE_COMMENT: 我是表解释
1 row in set (0.00 sec)
4,查询一张表的详细信息(包括字段注释,字段名称,类型等).
use information_schema;
select * from information_schema.columns where table_schema =‘你的表所在的数据库‘ and table_name = ‘你的表名‘;
mysql> mysql> SELECT * FROM COLUMNS WHERE table_schema=‘test‘ AND table_name=‘test1‘\G
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: test1
COLUMN_NAME: tt
ORDINAL_POSITION: 1
COLUMN_DEFAULT: NULL
IS_NULLABLE: YES
DATA_TYPE: int
CHARACTER_MAXIMUM_LENGTH: NULL
CHARACTER_OCTET_LENGTH: NULL
NUMERIC_PRECISION: 10
NUMERIC_SCALE: 0
DATETIME_PRECISION: NULL
CHARACTER_SET_NAME: NULL
COLLATION_NAME: NULL
COLUMN_TYPE: int(11)
COLUMN_KEY:
EXTRA:
PRIVILEGES: select,insert,update,references
COLUMN_COMMENT: 我是解释
GENERATION_EXPRESSION:
1 row in set (0.00 sec)
mysql>
注:还有一种方式:
# 查看建表语句，可以看到你的表注释与字段注释
show create table table_name;
mysql> SHOW CREATE TABLE test1\G
*************************** 1. row ***************************
Table: test1
Create Table: CREATE TABLE `test1` (
`tt` int(11) DEFAULT NULL COMMENT ‘我是解释‘
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT=‘我是表解释‘
1 row in set (0.00 sec)
mysql>
# SHOW 方式可以查看你的字段注释
show full columns from 表名;
mysql> SHOW FULL COLUMNS FROM test1; +-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+ | Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment | +-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+ | tt | int(11) | NULL | YES | | NULL | | select,insert,update,references | 我是解释 | +-------+---------+-----------+------+-----+---------+-------+---------------------------------+--------------+ 1 row in set (0.00 sec) mysql>
所以总结来看，如果想查看表与字段的信息，最好通过建表语句来看。
就是SHOW CREATE TABLE xxx，这个最方便
